A turbine stator blade is a component that is provided in a flow path of a combustion gas from a combustor in a gas turbine engine. FIG. 1 illustrates an example of an existing turbine blade 30. The turbine blade 30 includes a plurality of blades 31 which are disposed about the axis of the turbine at intervals in the circumferential direction, and bands 32 which support both ends of each blade 31 and extend in the circumferential direction.
Since the surface of the turbine stator blade 30 is exposed to a hot combustion gas (mainstream gas) 34 discharged from a combustor, the surface of the turbine blade needs to be prevented from being damaged by the heat. For this reason, the inside of the blade is cooled by cooling air, and film cooling is performed to cool the surfaces of the blade and the band such that cooling air is blown out from cooling holes provided in the blade and the band to form a layer of the cooling air. Since the turbine stator blade has a complex structure to perform such film cooling, manufacturing costs become high. Further, since a part of high-pressure air contributing to the thrust force is used as cooling air, there is a loss in the thrust force.
On the other hand, in an airplane engine, since the output and efficiency of the turbine may improve by increasing the temperature of a combustion gas, an increase in the temperature of the combustion gas is important for high performance of the airplane engine. Further, there is a need to decrease the weight of the components for high performance of the airplane engine. For this reason, a study has been conducted which attempts to use a ceramic matrix composite material (CMC: Ceramic Matrix Composites) as a material for forming the turbine stator blade, where the CMC has a benefit in that the heat resistance is superior to that of the metallic material and the specific gravity is smaller than that of the metallic material.
The CMC is a composite material of fiber fabric and ceramic, and in order to maintain the strength, the fiber fabric needs to be disposed in the smaller parts of components. The blade with the film cooling structure has a complex structure. Further, in the blade and the band, the constitution direction of the fiber fabric are different in accordance with the requirements of function and strength. For this reason, it is difficult to integrally form the portions of the blade and the band from the fiber fabric using the current technique. For this reason, a technique is adopted which separately manufactures the blade and the band and fastens both to each other to form a turbine stator blade.
However, since the strength of the CMC is smaller than that of metal, there is a need to prepare a countermeasure for alleviating a concentration of stress in the bonded portion when the components formed of CMC are bonded to each other. Further, when a gap is formed in the fastened portion, the mainstream gas may leak from the gap. For this reason, there is a need to prepare a countermeasure for reducing the leakage.
Incidentally, Patent Document 1 below discloses a background art in which a blade and a band are separately manufactured and both are fastened to each other to form a turbine blade.
FIGS. 2A and 2B are cross-sectional views illustrating a turbine blade 40 disclosed in Patent Document 1. In FIGS. 2A and 2B, a blade 41 and a band (a platform) 42 are separately manufactured components, and both are bonded to each other to form the turbine blade 40. In FIG. 2A, the blade 41 and the band 42 are fastened to each other by mechanical fastening means (a bolt, a clamp, a pin, or the like) 43 penetrating both. In FIG. 2B, the blade 41 and the band 42 are fastened to each other by a reinforcement member 44 with a U-shaped cross-section.